Photosensors are widely used in modern society, including in digital camera sensors, scanner, optical communication elements, fire detectors, and so on. It is a long-felt need in this art to develop photo sensors being better responsive to some certain wavelengths. For example, the detection of different colors (which are usually the primary colors of red, green and yellow) by digital camera sensors is processed via applying different color filters, which increases cost but reduces the responsivities to light within certain spectrum.
Another kind of element that is usually used in photo-detecting is the diode. When a voltage applied across a junction of the diode is reverse biased, a depletion region would be formed at the junction. The depletion region has a well ability to store the energy absorbed from light as electron-hole pairs, and the greater thickness the junction has, the shorter wavelength the light absorbed will be. The diode's surface could be further processed to decrease the responsivity to short wavelengths, which makes the silicon-based diode has a responsivity to light mainly within the spectrum of near-infrared. The silicon-base P-N diodes are low-cost, and the traditional photo diodes usually adopt N-well P substrate as basic structures. Although the traditional silicon-based P-N diodes have a well responsivity to light within the spectrum of the infrared, especially the near infrared, they don't have an ideal responsivity to the visible light, especially bad to light of the short wavelengths (450 nm-550 nm).
In order to overcome the drawbacks in the prior art, a method for photo-detecting and an apparatus for the same are provided. The particular design in the present invention not only solves the problems described above, but also is easy to be implemented. Thus, the invention has the utility for the industry.